The invention relates to a heat exchanger arrangement for an internal-combustion engine.
This invention is based on Published European Patent Application EP 1 249 580 A1. In EP 1 249 580 A1, an internal-combustion engine is described which has a heat engine operating according to the Rankine process. The heat engine converts hot steam of a working medium by means of an expansion device to kinetic energy, which can be coupled into the output of the internal-combustion engine for reducing the fuel consumption and/or for increasing the power of the internal-combustion engine. For this purpose, the heat engine has a high-temperature circuit and a low temperature circuit. A heat exchanger is provided for the low-temperature circuit. By means of this heat exchanger the coolant of the internal-combustion engine is cooled and the thermal energy is transmitted to the working medium. A pump is provided for delivering the working medium. An additional pump arrangement is provided for the high-temperature circuit, which pump arrangement delivers the working medium through a further heat exchanger, which is arranged in the hot exhaust area of the internal-combustion engine. The thus produced hot steam from the low-temperature circuit and the high-temperature circuit is subsequently fed to an expansion device, which converts the kinetic energy of the hot steam to kinetic energy. Subsequently, the working medium is liquefied in a condenser and is returned to the low-temperature and the high-temperature circuit.
Even when the arrangement of the internal-combustion engine and the heat engine of the above-mentioned type have no specific disadvantage, the present invention improves the efficiency of the overall system.
According to the invention, a heat exchanger arrangement is provided for an internal-combustion engine having a heat engine which converts hot steam of a working machine, by way of an expansion device, to kinetic energy. The working medium, that can be delivered by a pump, is heatable in a first heat exchanger by a coolant and in a second heat exchanger by an exhaust gas of the internal-combustion engine. In the delivery direction, the working medium first flows through the first heat exchanger and, subsequently, through the second heat exchanger, wherein the exhaust gas can flow through the first heat exchanger.
As a result of the arrangement according to the invention, the heat transfer-from the coolant of the internal-combustion engine and the exhaust gas of the internal-combustion engine-to the working medium is clearly improved in comparison to the state of the art. This increases the efficiency of the overall arrangement.
A further improvement of the efficiency is achieved by the arrangement wherein in the first heat exchanger, a first heat transfer device is arranged for the exhaust gas and the working medium, and a second heat transfer device is arranged for the coolant and the working medium. The working medium can flow in parallel through the first and the second heat transfer device or the working medium can flow successively through the first and the second heat transfer device. In that regard, the working medium can first flow through the second and subsequently through the first heat transfer device.
In a preferred embodiment, bypasses are provided by which the thermal flow of the exhaust gas and the coolant into the working medium in the first heat exchanger can be optimally controlled or optimally automatically controlled.
In a further preferred embodiment, a third heat transfer device for the exhaust gas and the working medium is arranged in the second heat exchanger, and a fifth bypass for the working medium is provided in the second heat exchanger, wherein the thermal flow can be automatically controlled from the exhaust gas into the working medium in the second heat exchanger.
The efficiency of the heat engine is improved again in that a third heat exchanger is arranged in the flow direction of the working medium behind the second heat exchanger.
By arranging a fourth heat transfer device for the working medium and the exhaust gas in the third heat exchanger, and providing a sixth bypass for the fourth heat transfer device, the thermal flow can be adjusted particularly well from the exhaust gas and from the coolant into the working medium in the third heat exchanger.
In a further preferred embodiment, an injection device for the working medium is arranged in at least one of the heat transfer devices, in which case a very fast automatic temperature control can be achieved in the heat transfer devices.
In yet another preferred embodiment, an auxiliary heater for the working medium is provided in at least one heat exchanger, by which the working medium can be heated up rapidly.
In yet another preferred embodiment, at least one second second heat exchanger and/or one second third heat exchanger is provided in a flow direction of the working medium behind the second heat exchanger, in which case the efficiency of the heat exchanger arrangement is further improved.
In yet another embodiment, the second heat exchanger is an exhaust gas purification system, in which case a particularly compact and highly integrated design can be achieved.
In a further embodiment, the exhaust gas and/or the coolant can flow through the heat exchangers according to the counter-current principle with respect to the working medium, which also has a positive effect on the efficiency of the heat exchanger arrangement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.